Neuromodulation is extremely important as it can govern the way neurons interact with one another. This is true from the simplest to the most complex neural processes, be it locomotion or emotion. Investigations into vertebrate neuromodulation to date have primarily used pharmacological tools, where drugs are bath applied and their cellular and synaptic consequences are monitored electrophysiologically. However, these studies provide no direct information about the activity patterns of the cells that contain these chemicals or what the real behavioral consequences of that activity may be. This research project plans to gain unprecedented access to neuromodulation in a vertebrate preparation using the elegant imaging and genetic tools available in the zebrafish, Danio rerio. The zebrafish is poised to become a powerful model system in all aspects of motor control and its development and this project intends to capitalize on its advantages by focusing on the role of descending modulatory centers. Thus, the aim of this proposal is three-fold: 1) to identify and catalogue the development of three potential neuromodulators, serotonin, dopamine and noradrenaline, 2) to visualize the activity of their respective neurons during elicited axial motor behaviors, and 3) to perturb the activity of these neurons in vivo and monitor the behavioral consequences.